1. Technical Field of the Invention
The present invention concerns a procedure for testing a potentially-active substance used in the hair-care field.
The term "hair-care field" encompasses everything related to the hair of an individual.
Accordingly, the expression "potentially active substance used in the hair-care field," or, in the remainder of the text, the term "substance" signifies any molecule or set of molecules producing potential activity in the hair-care field and, in particular, any molecule or set of molecules potentially producing an effect on the survival, slowing or stoppage of growth, loss by falling, or aggravated growth of the hair follicles. The substance to be tested can be used according to the invention procedure either in molecular form or as a composition containing the molecule to be tested.
2. Description of the Prior Art
At present, prior art cites two principal methods for testing a potentially-active substance in the hair-care field.
The first consists in performing trials on volunteers and in noting relatively rapidly the effects produced by the tested substance. This method obviously presents many disadvantages, including, in particular, that of dealing with humans, thereby obviously restricting the scope of application of this method for ethical reasons. As a result, the number and quality of the substances tested is limited. Furthermore, these tests require burdensome implementation procedures and are conducted over long periods of time. In most cases, the test results entail observations of phenotypical modifications of the hair follicles
The second method known according to prior art is described in Patent No. EP-434,319. It includes dissection of the hair follicle and involves taking a skin sample containing follicles, cutting the hair shaft beneath the dermal/epidermal junction, then in isolating the follicle from the surrounding skin without damaging the bulb. One modification of this method as suggested by Williams and Stenn (Dev. Biol., 165, 469-479 (1994)) consists in preliminarily cutting the biopsy into thin vertical slices 1 mm thick, then in performing the dissection according to the technique described in Patent No. EP-434,319, by pulling the follicle from its environment using tweezers.
This second method and the variant thereof require the preservation of all of the characteristics making the hair follicle viable, that is, those characteristics capable of regenerating a hair shaft in vitro (on this subject, see Science des traitements capillaires, Charles Zviak, Masson, 1987, in which these characteristics are described). Accordingly, the follicle must be preserved, most notably along with its bulb and dermal papilla. This can be achieved only by meticulous dissection, a process which makes implementation of the procedure burdensome. It will be easily understood that, in terms of usable, viable hair follicles, the yield from such dissection is extremely small.
The Applicant thus sought a new procedure for testing a potentially-active substance used in the hair-care field and which preserves the efficacy of conventional methods while facilitating implementation of the procedure.